Surefire does not support tests or any referenced libraries calling System.exit() at any time. If
they do so, they are incompatible with Surefire and you should probably file an issue with the library/vendor.
Alternatively the forked VM could also have crashed for a number of reasons.
Look for the classical "hs_err*" files indicating VM crashes or examine the Maven log output
when the tests execute. Some "extraordinary" output from crashing processes may be dumped to the console/log.
If this happens on a CI environment and only after it runs for some time, there is a fair chance your test suite is
leaking some kind of OS-level resource that makes things worse at every run. Regular OS-level monitoring tools
may give you some indication.

There is a specific gwt-maven-plugin at codehaus, but if you want to run
with Surefire, you need the following settings:

Use the following configuration:
<useSystemClassLoader>true</useSystemClassLoader>
<useManifestOnlyJar>false</useManifestOnlyJar>
<forkCount>1</forkCount>
Try reuseForks=true and if it doesn't work, fall back to reuseForks=false